Ultraman Australia race director Tony Horton said the organisers tried to find a balance with competitors — young and old, female and male, first-timers and established "ultramen" — when selecting the entrants.

Krista Page, 43, said being one of the few women to apply "probably gave her a little bit of an edge" with selection.

Mark Heaysman, 58, is competing alongside his 35-year-old son Dane, and said he believed their relationship helped them to stand out among the hopeful competitors that applied.

Mr Horton said he hoped next year's Ultraman — there will be one, according to him — will see an even more varied array of applicants, now that people see it can be done.

"No-one believes the distances, they kind of shake their head when you tell them what the distances are," he said.

"I think people didn't think we were serious, they didn't think we were going to put this race on."

But the distances are doable and the race is on, as evidenced by those 37 athletes who were pulling their wetsuits up, testing the gears on their bike and doing more than a few stretches before the ultimate run.